TECHNICAL ANALYSIS // 13.07.2011
The wind tunnel is the heart of any Formula One development programme, where the most performance can be found in the most cost effective conditions. That means teams must be able to rely on a good, precise and accurate model to test new parts during the season…
The first time you enter the model shop, you might think you’ve jumped into another dimension where everything’s smaller. It is a little bit like a Formula One version of Gulliver's Travels!
The goal of the model shop is to create a 50% scale model of the car that is fit for use in the wind tunnel. Hundreds of parts, designed by the aerodynamic team, will be manufactured at the factory for the model only, all using a variety of different processes.
The reason behind the 50% scale model testing, at times when teams like MERCEDES GP PETRONAS are fully equipped with a full-scale wind tunnel, comes from the FOTA Resource Restriction Agreement, which limits full-size wind tunnel testing to 4 days around the year. When operating at 50% scale, you can also make new parts faster and cheaper for testing, than with a full size car; indeed, all teams operate at either 50% or the maximum permitted by the FIA, 60% scale.
The materials that are used to build a model are different to what will be used on the car, and the processes that we use to create a model vary depending on the part. In some cases the processes are traditional machining such as lathe work and milling machines, and in other cases rapid prototyping will be used. The Rapid prototyping processes used in house are stereolithography (SLA) and Laser Sintering (SLS). Both are termed ‘additive layer manufacturing’.
Stereolithography (SLA) uses a UV laser to cure a photopolymer into a solid part and “selective laser sintering” uses a nylon based material to manufacture parts which need to be more durable because of the high loads involved. Less loaded areas such as bodywork, floors and diffusers will made using rapid prototyping.
The advantage of the technology is to turn a computer-generated model into a physical model in a short space of time, which allows the manufacture of iterations of designs very quickly. The material differs from carbon fibre as it is much less stiff, and can therefore only rarely be used on the full size car, but still good enough for use on the scale model.
How do parts go from the computer to the tunnel?
The parts are designed on computers and then released to the model shop, at which point the model shop has a time scale to manufacture them using machining, rapid prototyping and some composite techniques. The model makers will then have time to fit these new parts onto the model. This process continues in a cycle providing a constant flow of work for the model shop!
Once assembled the model will go into the wind tunnel and be tested 24 hours a day, 7 days a week. It is therefore a very fluid process where alterations feed through to the aerodynamicists, are relayed back to the designers and eventually signed off for full size production for a race weekend. On average the team will test 100 new parts per day in the Wind Tunnel.
The aerodynamic team is split into groups responsible for different areas of the car. These different teams will go into the wind tunnel for a period of time, where they will be able to concentrate on their specific area of expertise.
A constant search for new technology…
The model itself is a very intelligent piece of kit that has a number of applications outside of the obvious aerodynamic wind tunnel tests. It can be used to measure forces internally on the model, to measure aerodynamic load or to monitor the suspension characteristics and how it reacts with the bodywork in certain directions or pitch.
Innovations on the full-size cars can represent a challenge for the model and the model shop team – the best examples being last year’s F-duct and some of the work done on the exhaust system. These kinds of systems represent real challenges to incorporate into the model, and this drive to innovate means the model shop is constantly looking for new technology to enhance the manufacturing process.
While the season is progressing and the team needs updates and more aerodynamic performance, the model from the current season would be used to implement these changes. At some point during the season the focus will be switched to the development of next season’s car. This means working on early concepts and into the next season.
Quick Facts:
• Rapid prototyping: automatic construction of physical objects using additive manufacturing technology.
• Stereolithography: Stereolithography (SLA) uses a UV laser to cure a photopolymer into a solid part and “selective laser sintering” uses a nylon based material to manufacture parts which need to be more durable because of the high wind resistance involved. Less strained areas like body work, floors and diffusers will be rapid prototyped.
• The model built in the model shop would be a 50% model of the car, in a configuration more advanced than what is in use at the track.
• On average the team will test 100 new parts per day in the Wind Tunnel.
(With thanks to Richard Bruce and the Model Shop)
Credit: Mercedes GP (www3.mercedes-gp.com)
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